• Journal of Ocean Engineering and Technology
• /
• v.30 no.2
• /
• pp.69-74
• /
• 2016

A new wave-piercing-type high-speed planing boat without a chine was developed, and its basic performance was investigated in a model test, including the resistance, trim, and sinkage. The maximum speed of the developed ship was 35 knots. The hull form was developed by combining a VSV (very slender vessel) and TH (transonic hull), which have large deadrise angles at the bow. The main dimensions were estimated by a statistical approach using actual ship data. The effect of a side fin attached at the stern near the water line was investigated from a resistance point of view. It was found that the developed hull form showed the possibility of a new concept for a high-speed planing hull without a chine, and the side fin played an important role in increasing the resistance performance by controlling the trim and sinkage in the high-speed range.

• Journal of Mechanical Science and Technology
• /
• v.17 no.12
• /
• pp.2116-2124
• /
• 2003

An experimental study providing additional knowledge of quasi-conical symmetry in swept shock wave/turbulent boundary-layer interactions is described. When a turbulent boundary layer on the flat plate is subjected to interact with a swept planar shock wave, the interaction flowfield far from fin leading edge has a nature of conical symmetry, which topological features of the interaction flow appear to emanate from a virtual conical origin. Surface streakline patterns obtained from the kerosene-lampblack tracings have been utilized to obtain representative surface features of the flow, including the location of the virtual conical origin. The scaling law for the sharp-fin interactions suggested by previous investigators has been reexamined for different freestream Mach numbers. It is noticed that the scaling law reasonably agrees with the present experimental data, however, that the law is not appropriate to estimate the location of the virtual conical origin. Further knowledge of the correlation for the virtual conical origin has thus been proposed.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.8
• /
• pp.609-615
• /
• 2021

Three-dimensional numerical study was carried out to evaluate the aerodynamic characteristics of the supersonic grid fins installed on SpaceX Falcon 9. The present three-dimensional flow results were compared to the results by the concept of the unit grid fin previously introduced for more efficient and simpler flow calculations, and the validity of the approach of the unit grid fin were evaluated. The aerodynamic characteristics in supersonic flights Mach 2.8 of SpaceX Falcon 9 with various angle of attacks were also obtained.

• 한국전산유체공학회:학술대회논문집
• /
• 2011.05a
• /
• pp.141-147
• /
• 2011

A two-phase numerical model for plate-fin heat exchangers with plain fins and wave fins is studied incorporating the thermodynamic properties and the characteristics of fluid flow. The numerical simulations for the two fins in cryogenic conditions are earned out by employing a homogenous two-phase flow model with the CFD code ANSYS CFX. The heat transfer coefficients and the friction factor for nitrogen saturated vapor condensation process inside two types of plate fin heat exchanger are evaluated including the effects of saturation temperature (pressure), mass flow rate and inlet vapor quantity. The convective heat transfer coefficients and friction factors will be used for design of plate-fin type heat exchangers operating under cryogenic conditions.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2003.10a
• /
• pp.60-63
• /
• 2003

Resistance performance of 3 G/T class coastal leisure boat is experimentally investigated at high speed ranges and the effect of a fin attached at hull side is studied together. Wave patterns are observed to make clear the relation between the resistance performances and the wave characteristics.

• Journal of Korea Foundry Society
• /
• v.7 no.1
• /
• pp.28-37
• /
• 1987

The progression of the solidification wave front in V-section and finned casting was studied by use of the pour-out test, employed with high. Purity aluminum. The results obtained were as follows; a) The shape of solidification wave front at the inside and outside corners did not change according to solidification time, but it changes according to the corner angles at a given molding and melting condition. b) The cooling fin effect could be repserented as functions of solidification time and fin sise, and this result could be applied to enhance the accuracy of the section modulus method in the design of T and V section.

• Journal of Ocean Engineering and Technology
• /
• v.22 no.3
• /
• pp.58-63
• /
• 2008

A 32-ft class leisure boat was newly developed using statistical analysis of actual ships. Resistance performances were investigated by testing models in a high-speed circulating water channel, and with the CFD method. The effects of a trim tab and of a fin attached at the hull side were studied together. Wave patterns were observed to clarify the relationship between resistance performance and wave characteristics. It was found that a trim tab and a side fin play a role in increasing resistance performance within a certain velocity range.

• International Journal of Ocean System Engineering
• /
• v.3 no.1
• /
• pp.10-15
• /
• 2013

A ship cruising in the ocean oscillates continuously due to wave action. In order to reduce the ship's roll, we developed a fin stabilizer as an anti-rolling device for a 500-ton-class high-speed marine vessel. During the development phase, it was necessary to set up control gains for the motion and hydraulic systems and assess the effectiveness of the anti-rolling performance on the ground. For this reason, a Target Simulator, which simulated the ship's motion, was given operator inputs such as the engine telegraph and waterjet deflection angle, and generated roll using a one-degree-of-freedom motion base. Hardware-In-the-Loop Simulation (HILS) was performed using the Target Simulator in order to confirm the various logics of the developed fin stabilizer, select initial control gains, and estimate the anti-rolling performance. In conclusion, it was confirmed that HILS was very helpful to develop the fin stabilizer because it could reduce the number of sea trial tests that were needed and could find many malfunctions in the factory a priori.

• Journal of Venture Innovation
• /
• v.4 no.2
• /
• pp.77-95
• /
• 2021

In the midst of the progress of the 4th industrial revolution, the Corona19 Pandemic was forming giant double wave. Companies riding this wave can win, but companies that do not will fall into the wave and struggle. In connection with the 4th industrial revolution, various technologies are emerging and commercialized. At this point, consumers, especially digital natives, who have been with digital since birth, tried to find out what factors affect the intention to use these technologies and which factors have the most important influence. For this purpose, data were collected through a survey on factors affecting the intention to use FinTech technology and AR technology for 150 digital natives in their 20s. Based on this, statistical analysis was conducted and the following results were obtained. As a result of the overall analysis regardless of the type of technology, it was found that performance expectancy, effort expectancy, social influence, and habits have a positive (+) effect on digital natives' intention to use the 4th industrial technology. On the other hand, a significant influence relationship between the facilitating conditions, hedonic motivation and intention to use the 4th industrial technology was not tested. It was found that the influence was greatly influenced by social influence and habits. In the case of FinTech and AR, which were further subdivided into this study, different aspects were revealed as a result of separate analysis. In the case of FinTech technology that emphasizes utilitarian value, performance expectancy, effort expectancy, social influence, and habits had a positive (+) effect on intention to use. It was found that the influence was greatly influenced by habits and social influence. In the case of AR, which emphasizes the hedonic value, all the variables adopted in this study had a positive (+) effect on the intention to use the technology. It was found that hedonic motivation and social influence had a great influence. Combining the results of the analysis, social influence was found to be an important influence variable regardless of the type of 4th industrial technology. FinTech technologies such as mobile banking, where services are becoming more common, are habits, and in the case of AR, which has not yet been universalized and is provided mainly for entertainment, hedonic motivation was found to be an important factor. This study was able to present academic and practical implications based on the above confirmation of factors affecting digital natives' acceptance and use of the 4th industry technology.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1034-1039
• /
• 2004

The row-by-row heat transfer characteristics of fin-and-tube heat exchangers having wavy fins were experimentally investigated. Three samples having different rows (one, two and three) were tested. Results show that the heat transfer coefficient is strongly dependent on the tube row. The heat transfer coefficient of the first row is larger than those of second or third rows. However, the difference decreases as the Reynolds number increases. The heat transfer coefficients of the second and the third row are approximately the same, probably due to increased mixing of bulk flow by wavy channels. Although samples have different tube row, the heat transfer coefficients of same row are approximately the same.